1. Field of the Invention
The present invention relates to a solid propellant rocket motor that utilizes a plurality of propellants and has the ability to start, stop and restart repeatedly and, in addition, control the attitude of the rocket in flight. The rocket motor is characterized in part by a high thrust in addition to a high impulse boost followed by a series of, on-demand, stop and restart metered or throttling operations.
2. Description of the Prior Art
The entire proplusive capability of solid propellant rocket motors is usually spent during the combustion of one solid propellant grain. This happens because once a grain of solid propellant is ignited it is difficult to stop the combustion process and the entire grain is normally consumed.
It has been proposed in the prior art to provide a solid propellant rocket motor with an ability to fire more than once, that is, a rocket motor with a "start-stop-restart" capability by providing two or more concentric units, that is, layers or zones of solid propellant in a combustion chamber with a flame inhibiting barrier separating the layers, the barrier being made of a material that will confine the burning to a single layer or zone, but which, nevertheless, is destructible so that the next adjacent layer may be ignited. The burning of each layer produces a thrust in the form of a discrete pulse.
One such arrangement for providing a rocket motor that may be fired more than once is disclosed in U.S. Pat. No. 3,293,855 granted on Dec. 27, 1966 to W. E. Cutill et al. wherein a pyrotechnic and an electrically ignitable film are provided between each of the layers for igniting, upon command, in turn, each of the next adjacent layers. Similarly, U.S. Pat. No. 4,357,795 granted on Nov. 9, 1982 to Thomas W. Bastian et al. discloses a solid rocket fuel with a plurality of fuel layers, each independently ignitable. The layered sections are capable of being placed end to end within a casing.
Other such arrangements are disclosed in U.S. Pat. Nos. 3,564,845 granted to I. H. Friedman et al. on Feb. 23, 1971 and 3,568,448 granted to G. E. Webb, Jr. on Mar. 9, 1971, wherein one of the two solid propellant concentric layers that are separated by a flame inhibiting barrier is ignited by an igniter that is extended through the rocket motor nozzle into the combustion chamber. The other layer is ignited by a gas generator that is connected by a tubular extension to the head end of the combustion chamber. A rupturable membrane seal and perforated support member assembly is provided to isolate the gas generator from the motor combustion chamber during burning of the first rocket propellant layer. U.S. Pat. No. 3,677,011 granted on Jul. 18, 1972 to C. W. Vickland discloses a dual thrust level rocket motor with restart capability including an oxidizer supply and plurality of injectors for delivering the oxidizer to the fuel grain. U.S. Pat. No. 3,677,010 granted on Jul. 18, 1972 to R. H. Fink et al. discloses a solid fuel rocket motor having a grain comprising a plurality of individual, concentric layers separated by a liner having insufficient oxidizer to sustain combustion. A liquid oxidizer that is hypergolic with the liner may be injected to ignite an exposed liner layer and the next adjacent propellant layer to extend the rocket's range. U.S. Pat. No. 3,457,727 granted on Jul. 29, 1969 to J. R. Munger discloses a solid fuel rocket motor utilizing a solid propellant and a liquid oxidizer injected in the rearward portion of the motor. U.S. Pat. No. 3,452,544 granted on Jul. 1, 1969 to R. L. Glick et al. discloses a solid propellant rocket motor with a single solid propellant grain having thrust boost-sustain and sustain-boost capabilities acheived with rocket motor mounted gas generator or quenching mechanisms.
U.S. Pat. No. 3,826,087 granted on Jul. 30, 1974 to Allan J. McDonald discloses a solid propellant rocket in which gas generators produce gases that are mixed and burned to produce thrust for the rocket.
U.S. Pat. Nos. 3,340,691 granted on Sept. 12, 1967 to G. F. Mangnum and 3,354,647 granted on Nov. 28, 1967 to W. C. Aycock disclose arrangements similar to each other involving the admission of liquid fuel to a combustion chamber for the destruction of a flame inhibiting barrier and the ignition of an adjacent layer of propellant.
All of the above prior art disclosures are characterized in the provision of a single combustion chamber for a plurality of concentric solid propellant layers of zones, involving the destruction of a flame inhibiting barrier between layers in order to initiate combustion in firing of the next adjacent layer, and in the use of a relatively complicated ignition arrangement for effecting destruction of the barrier and ignition of the adjacent layer. The Freidman, Jr. et al. and Webb, Jr. patents involve the use of a rupturable membrane and perforated support member which when ruptured and disintegrated, respectively, tend to introduce debris into the combustion chamber. The Mangum and Ayecock patents involve the admission of liquid fuel to the combustion chamber.
U.S. application Ser. No. 498,603, filed on May 26, 1983 by M. Fling et al. and assigned to the assignee of the present invention, discloses a solid propellant rocket motor that may be fired more than once and which involves the use of plural concentrically or tandemly fabricated combustion chambers which are separated by a perforated bulkhead and each of which contains an individually associated propellant. Pressure responsive membrane means positioned in a first one of the chambers' covers the perforation in the bulkhead to preclude communication between the chambers when a substantially higher pressure is present in the first one of the chambers than in an adjacent chamber and allows communication between the chambers when the pressures in the chambers is reversed.
Numerous other arrangements directed towards controlled flight of solid propellant rocket motors are disclosed in the prior art. Among these arrangements are the following U. S. Patents:
U.S. Pat. No. 3,811,380, J. P. Glass; PA1 U.S. Pat. No. 3,668,872, A. T. Camp et al.; PA1 U.S. Pat. No. 3,494,130, S. Zeman; PA1 U.S. Pat. No. 3,457,726, J. Trotel; PA1 U.S. Pat. No. 3,434,287, L. Caveny; PA1 U.S. Pat. No. 3,398,537, J. E. Picquendar; PA1 U.S. Pat. No. 3,349,565, A. E. Williams; PA1 U.S. Pat. No. 3,349,563, E. L. Taylor; PA1 U.S. Pat. No. 3,248,875, R. D. Wolcott; PA1 U.S. Pat. No. 3,266,237, C. J. Crowell et al.; PA1 U.S. Pat. No. 3,011,309, J. M. Carter;
Implicit in the foregoing discussion is an inherent limitation in all of the different types of solid propellant rocket motors discussed, i.e., the inability to provide a high thrust and/or high impulse boost pulse followed by a series of stop/restart throttling operations, on demand.